Add 'editor:edit-session-added' event to Editor

spec/app/editor-spec.coffee

@@ -193,12 +193,18 @@ describe "Editor", ->
       otherEditSession = rootView.project.buildEditSessionForPath()
 
     describe "when the edit session wasn't previously assigned to this editor", ->
-      it "adds edit session to editor", ->
+      it "adds edit session to editor and triggers the 'editor:edit-session-added' event", ->
+        editSessionAddedHandler = jasmine.createSpy('editSessionAddedHandler')
+        editor.on 'editor:edit-session-added', editSessionAddedHandler
+
         originalEditSessionCount = editor.editSessions.length
         editor.edit(otherEditSession)
         expect(editor.activeEditSession).toBe otherEditSession
         expect(editor.editSessions.length).toBe originalEditSessionCount + 1
 
+        expect(editSessionAddedHandler).toHaveBeenCalled()
+        expect(editSessionAddedHandler.argsForCall[0][1]).toBe otherEditSession
+
     describe "when the edit session was previously assigned to this editor", ->
       it "restores the previous edit session associated with the editor", ->
         previousEditSession = editor.activeEditSession

src/app/editor.coffee

@@ -388,6 +388,7 @@ class Editor extends View
     if index == -1
       index = @editSessions.length
       @editSessions.push(editSession)
+      @trigger 'editor:edit-session-added', editSession
 
     @setActiveEditSessionIndex(index)